Such magnets with their respective wheel pieces are utilized to control the arc generated between two workpieces which are welded together along an annular weld seam. These magnets are arranged, as a rule, radially with respect to the weld seam line, as for instance, in the arrangement according to German Pat. No. 30 18 199, (see U.S. Pat. No. 4,436,980). Their respective magnetic cores, each carrying a coil, have on each of their ends facing the seam line a curved recess, following the course of the seam line by covering the same almost completely, and bearing the pole faces.
In such devices for the magnetic arc welding, the pole faces form a cylindrical surface surrounding the weld seam. The shape of the cross section of this cylindrical surface corresponds to the weld seam line, which means to the outer cross section of the part to be welded, for instance, rings, tubes, caps, sockets, or other such various cross sections or various geometrical shapes. The shape of the cross section does not necessarily have to be circular. The axis of the cylindrical surface runs parallel to the axis of the part of the welded, respectively, can be identical therewith.
The disadvantage of welding with such devices however, is the contamination of the pole surfaces by weld splashes, which exert a negative influence on the arc path, result in irregular weld seams and create problems with the coil insulation. The pole faces have therefore to be cleaned constantly, at short intervals. In the case of partially or fully automated welding machines of this kind, an additional device for the removal of weld splashes is therefore required, usually a brushing system.